Nowadays, production environments utilize testing apparatuses to evaluate and to test a plurality of DUTs. A DUT testing apparatus has to be capable of testing each DUT independently without being influenced by the tests provided to another DUT in the testing apparatus. This is necessary to evaluate the behavior of the DUTs and to avoid interference between different DUTs that are tested in the testing apparatus. Disadvantageously, interference between two independent DUTs distort the testing results and increase measurement errors that lead to a false evaluation of the DUT's behavior under test conditions.
Thus, normally the DUTs in such an apparatus are electrically isolated to avoid such interference. A typical electrical isolation value between the different DUTs is approximately in the range of 60 dB or higher. Such an isolation value might be a customer's requirement to obtain a standardized procedure.
To assure the prohibition of such false evaluations due to disturbing interference between different DUTs, a higher isolation between each DUT is applicable. A higher isolation, such as dedicated shielding for each DUT, increases the costs for the evaluation of each DUT, raises the needed time for testing the DUT and thus raises the production costs. Thus, a higher isolation should be avoided.
To avoid the above-mentioned interference, it is also possible to assure that only one DUT is tested per given timeslot. Thus, the other DUTs have to be switched inactive until the evaluation and testing procedure of the active DUT is finished. Such an approach is very time-consuming in case a plurality of DUTs should be tested in a short period of time.
Another known approach is the use of separate testing plans in accordance with the frequency range that should be tested. Such separate testing plans are hard to maintain during the testing procedure since a plurality of independent test plans are required for each DUT. Additionally, only a limited number of combinations, such as two independent time-division-synchronous-code-division-multiple-access, TD-SCDMA, frequency bands, can be tested simultaneously because there are only two possibilities to arrange these TD-SCDMA frequency bands.
What is needed, therefore, is an approach for increasing the number of DUTs that can be tested simultaneously in a production environment, and to decrease the evaluation and test processing time, while minimizing or eliminating interference between the DUTs being tested simultaneously.
SOME EXAMPLE EMBODIMENTS
Embodiments of the present invention advantageously address the foregoing requirements and needs, as well as others, by providing methods and test apparatuses that facilitate simultaneous testing of an increased number of DUTs in a production environment, and a decrease in the evaluation and test processing time, while minimizing or eliminating interference between the DUTs being tested simultaneously.
In accordance with example embodiments, a method for testing at least a first device under test (DUT) and a second device under test (DUT) is provided. The method comprises determining whether a first radio frequency (RF) test signal from/to the first DUT interferes with a second radio frequency (RF) test signal from/to the second DUT. The method further comprises determining whether the second RF test signal from/to the second DUT interferes with the first RF test signal from/to the first DUT. The method further comprises predetermining whether at least a first measuring result obtained by applying the first RF test signal is disturbed above a first disturbance threshold value, and predetermining whether at least a second measuring result obtained by applying the second RF test signal is disturbed above a second disturbance threshold value. The disturbance threshold values may be predefined in testing procedures for testing the DUT. The method according to such embodiments thereby assures that a measuring result of a DUT is only valid in case an applied RF test signal does not disturb the measuring result of the DUT.
By way of example, a DUT may consist of any communication device that is capable of sending and receiving electrical signal over an air interface. By way of example, a DUT is a mobile communication device, such as a handheld user equipment (UE) of device (e.g., a smart phone or a portable computing device, such as laptop, tablet, etc.), or a radio communication device. Alternatively, the DUT is a stationary communication device, such as equipment that is related to a communications system. By way of further example, the DUTs are each of a configuration that makes it difficult to provide testing plans that assure a testing of each DUT individually without disturbing an adjacent DUT. By way of further example, the DUT may be a radio communication device used in a radio communication environment according to any of the radio frequency ranges from 3 Kilohertz to 300 Gigahertz.
The DUT may be employed in a wireless communication environment, such as a long time evolution (LTE) system, Universal Mobile Telecommunications System (UMTS), a Global System for Mobile Communications (GSM), or any such wireless communications system. Additionally and/or alternatively, the wireless communications system is a wireless local area network (WLAN), for example, according to any of the standards according to IEEE 802.11.
According to example embodiments, the transmission and reception behavior of such DUTs is evaluated. This is achieved by applying an RF test signal to the DUT and analyzing the frequency spectrum the DUT obtains and sends out using an analyzing device, such as a vector network spectrum analyzer (VNA). By way of example, an RF test signal is a signal that is applied to a specific DUT to identify its behavior, such as electromagnetic compatibility (EMC) that may cause electromagnetic interference (EMI). Further, to speed up the evaluation process by simultaneously testing a plurality of DUTs, according to example embodiments, the testing is performed in a manner whereby one DUT does not interfere or distort the measurement results of another DUT being simultaneously tested.
According to a further embodiment, one or more of the first measuring result and the second measuring result is an error vector magnitude (EVM) value or a bit error rate (BER) value or a received signal strength indication (RSSI) value. The EVM, BER and RSSI values as first measuring result and/or second measuring result are used to classify the DUT according to standards requirements and to assure a normal behavior of the DUT under real conditions.
According to a further embodiment, one or more of the first measuring result and the second measuring result is a power value. By way of example, the power value is either an adjacent channel power (ACP) value or an adjacent channel leakage power ratio (ACLR) value. The ACPR is a ratio between the total power of an adjacent channel, such as an intermodulation signal to its main channel's power, the useful signal. There are at least two ways of measuring the ACPR. The first way is by finding 10*log of the ratio of the total output power to the power in adjacent channel. The second method is to find the ratio of the output power in a smaller bandwidth around the center of carrier to the power in the adjacent channel. The smaller bandwidth is equal to the bandwidth of the adjacent channel signal. Second way is more popular, because it can be measured easily. ACPR is desired to be as low as possible. A high ACPR indicates that significant spectral spreading has occurred. These power values classify the DUT to assure that subsequent channels in a communication system are not disturbed when using such a DUT. Since the communications systems in nowadays standards comprise multi-frequency- and multi-coding-algorithms, it is preferred to assure that a DUT that functions according to such a standard does not interfere with channels that the DUT is not allocated to.
According to a further embodiment, the method further comprises testing the first DUT and the second DUT simultaneously when both the first threshold value and the second value are undershot. In case the undershot is recognized, it is assured that the isolation between the first DUT and the second DUT is high enough and the measuring results do not interfere. According to an alternate embodiment, the method further comprises testing the first DUT and the second DUT sequentially when at least one of the first threshold value and the second threshold value is exceeded. It is sufficient if one of the threshold values is exceeded. This avoids interference between the DUTs in the testing apparatus and to assure that the measuring results are not faulty or tampered.
According to a further embodiment, the method further comprises determining of an isolation value between the first DUT and the second DUT, and storing the isolation value as an isolation matrix. By way of example, the isolation value is a power isolation value that is achieved by measuring the received power value at a first DUT and measuring the transmitted power value of the second DUT. Since these isolation values are dependent on the testing apparatus and the slot at which the specific DUT is arranged at, it is helpful to apply an isolation matrix in order to recognize these specific isolation values.
According to further embodiments, the number of DUTs is greater than two so that a plurality of DUTs (e.g., tens of DUTs) can be evaluated and tested simultaneously.
In accordance with additional example embodiments, a testing apparatus is provided for testing at least a first DUT and a second DUT. The apparatus comprises a first terminal for connecting a first DUT, a second terminal for connecting a second DUT, a signal generating unit, and a central processing unit. The central processing unit is configured to (1) determine whether a first radio frequency (RF) test signal from/to the first DUT interferes with a second radio frequency (RF) test signal from/to the second DUT, (2) determine whether the second RF test signal from/to the second DUT interferes with the first RF test signal from/to the first DUT, (3) predetermine whether at least a first measuring result obtained by applying the first RF test signal is disturbed above a first disturbance threshold value, and (4) predetermining whether at least a second measuring result obtained by applying the second RF test signal is disturbed above a second disturbance threshold value. For example, the test apparatus consists of a testing rack at which a plurality of DUTs can be connected.
By way of example, the central processing unit keeps track of all resource allocation requests of each DUT. It maintains an isolation value matrix with isolation between the different terminals. For each spectrum or resource allocation, the conflict of measuring results is advantageously checked. This is achieved by applying a central processing unit in the measurement apparatus to identify a threshold value that is above or below a certain disturbance threshold value.
According to one such example embodiment, the signal generating unit is arranged external from the testing apparatus and is connected to the apparatus via a third terminal.
According to further embodiments, the signal generation unit generates signals of higher complexity, such as modulated and coded RF test signals, which may be employed in the above mentioned communications systems. By way of example, the signal generating unit is configured to generate CDMA, FDMA and/or TDMA signals that might be coded using different analog or digital modulation schemes, such as QAM, QPSK or OFDM.
According to further embodiments, a measuring device is connected to a fourth terminal of the apparatus. Thus, the apparatus is only an instance having the central processing unit for allocating the resources to the different DUTs that are connected to the specific terminal. By way of example, the signal generation and the analyzing of the measured signals is done externally by a multi-functional device or by a specific vector network analyzer (VNA).
According to further embodiments, the central processing unit is configured to allocate a resource range for each DUT. By way of example, the resource range for each DUT consists of a frequency spectrum range. By allocating each DUT to a specific frequency range via the central processing unit, the transmitting frequencies and the receiving frequencies can be considered in parallel. In case no interference is obtained, since the transmitting frequencies and the receiving frequencies comprises a frequency gap, the DUT can be tested in parallel. In case the DUTs interfere, which might be predetermined using the central processing unit of the apparatus, the second DUT needs to wait until the first DUTs test sequence is finished and the frequency range is available.
Since all DUTs typically use the same and identical test plan, all DUTs reach the same frequency nearly at the same time. Measurements with limited dynamic range requirements are blocked even if they could be executed for multiple DUTs at the same time. Thus, the central processing unit can be configured to keep track of all RF transmissions which refer to transmitting and receiving transmissions. An isolation value between the terminals is known, especially using the isolation matrix, and the transmitted power of block can discover all power between the different DUT terminals.
According to further embodiments, the frequency resource allocation collision is checked in two ways, meaning that the relationship between the first DUT and the second DUT is tested and the relationship between the second DUT and the first DUT is tested as well to identify interference problems and an undershooting of the disturbance threshold values.
According to further embodiments, the central processing unit is configured to allocate the signal generator unit first and is further configured to subsequently allocate the measurement device. This avoids deadlocks and allows a fixed order of resource allocations. If spectrum or resources are to be allocated in parallel to the signal generating unit and the analyzing unit an order for allocating the resources to the generator first and the analyzer subsequently may be unattainable. Accordingly, a further approach is to allow a generator to allocate the recourses before the analyzer and to allow a spectrum after the instrument. Thus, generator and analyzer can work in parallel and only the analyzer is conflicted, which might be discovered at a later stage.
Still other aspects, features, and advantages of the present invention are readily apparent from the following detailed description, simply by illustrating a number of particular embodiments and implementations, including the best mode contemplated for carrying out the present invention. The present invention is also capable of other and different embodiments, and its several details can be modified in various obvious respects, all without departing from the spirit and scope of the present invention. Accordingly, the drawing and description are to be regarded as illustrative in nature, and not as restrictive.